The water stored in the water tank of a water closet is flushed into toilets or urinals every time they are used and flows through the entire inner surface thereof. Many chemical solution distributing apparatuses for distributing chemical solutions into the water in water tanks periodically and at a fixed amount to clean toilets or urinals every time water is flushed have been proposed.
For example, an apparatus which has the following configuration is known (e.g. refer to Patent document 1). A tubular and bottomed main body part which opens at a lower part thereof is set inside a water tank so that the opening at the lower end is positioned above the water surface in a condition where the water in the water tank is drained. At the same time, a chemical solution tank where chemical solutions are stored is installed outside the water tank; a liquid-drawing tube one end of which is opened at the upper part of the main body part while the other end is submerged in the chemical solutions in the chemical solution tank is provided; and moreover, a check valve which releases the air inside the main body to the outside is installed at the top surface of the main body part.
In this apparatus, when water is added to the water tank to raise the water level therein, water enters the main body from the opening at the lower end of the main body part and also raises the water level inside the main body part while releasing air inside the main body to the outside via a check valve. When the water inside the water tank is drained, the water level inside the water tank drops and the water level inside the main body part also nearly drops. However, since it is not possible to aspirate air from the outside to the inside of the main body part due to the action of the check valve, the pressure in the upper space part inside the main body part becomes negative. Then chemical solutions inside a chemical solution tank are drawn into the main body part via the liquid-drawing tube. The drawn chemical solutions drop into the inside of the main body and drip into the water inside the main body. When the water level outside the main body part becomes lower than the level of the opening at the lower end of the main body part, air flows into the main body part from the opening and the drawing of chemical solutions via the liquid-drawing tube stops. The above processes are repeated regularly every time water is supplied to or drained from the water tank and an almost constant amount of chemical solutions are drawn into the main body side from a chemical solution tank each time.
Additionally, an apparatus which has the following configuration is known (e.g. refer to Patent document 2). Inside a container which opens at its lower end and which is cup-shaped, a water-storage tank section where chemicals, which dissolve in water to generate chemical solutions, are retained and which also has an opening close to the lower end of this cup-shaped container is provided integral to the container so as to be placed at an upper part of the container. The container and water-storage tank are installed in the apparatus so as to be submerged completely inside a water tank.
In this apparatus, air vent holes are provided in the water-storage tank and when the water level inside the water tank rises, although water does not enter inside the cup-shaped container and thus chemicals are not submerged, air is ejected from the air vent holes and the water-storage tank is filled with water. When the water inside the water tank is drained and the water level therein drops, the water inside the water-storage tank section is jetted into the inside of the container from the opening due to gravitational force. By setting the position and direction of the opening so that the chemicals receive the jetted water, part of chemicals is dissolved and chemical solutions drip into the water tank.    Patent document 1: Utility Model Laid-Open Application No. Hei 6-30284 (FIGS. 1 to 4)    Patent document 2: Japanese Unexamined Patent Application, First Publication No. Sho 62-248725 (FIGS. 5 to 8)